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SPECIES DIVERSITY OF LEAF-LITTER ARTHROPODS AND VERTEBRATES IN A COSTA RICAN AGROECOSYSTEM MOSAIC**

Abstract

Understanding how land use affects species diversity and the microgeographic distributions of species is critical for adequate conservation planning and management. Ecosystems with high biodiversity are often under pressures resulting from conversion of natural ecosystems to alternative uses such as agriculture, livestock production, and timber harvest. We tested the effects of land use on communities of terrestrial leaf-litter fauna in the agroecosystem mosaic at the University of Georgia-Costa Rica campus at San Luís de Monteverde, Costa Rica. Originally covered with humid montane forest, the region now includes land converted to agriculture (coffee, mixed agriculture) and livestock production. We sampled leaf litter invertebrates (mainly arthropods) and small vertebrates (frogs, lizards, snakes, mammals) in four habitats within this mosaic: old growth forest (> 40 years with minimal disturbance), pasture/forest ecotone, pasture, and coffee plantation. We set arrays of pitfall traps associated with drift fences to capture animals occupying the leaf litter community at each site, checking traps twice per day. We also measured leaf litter cover and recorded qualitative environmental data (canopy cover, soil moisture). Over all sites, ants (Formicidae) were the most abundant arthropods (34%) followed by Diptera (22%), Coleoptera (13%), and spiders (13%). We found significant differences in capture rates between forest, ecotone, and coffee habitats compared to pasture for spiders, opiliones (harvestmen), and beetles (all more abundant in the former habitats). Among vertebrates, frogs and rodents were found only in forest and ecotone habitats. These results suggest that conversion of forested land to pasture results in loss of significant components of the leaf litter fauna. Conversely, ecotones maintain some of that diversity when patches of intact forest are included within the regional mosaic. We further explore the effects of leaf litter depth, nocturnal versus diurnal sampling, and microenvironments on the diversity of the leaf litter fauna.

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